Treatment of hydrocarbon gases



May 21, 1946, `.1. G. ALTHER *TREATMENT 0F HYDROCARBON GASES original Filed June 17; 19,39

QNNNSEM.

' fractions produced Patented May 2i, 1946 Joseph w No.

The invention relates particularly to the treatment o f hydrocarbon gases produced in connection with the reilning of crude petroleums, with the object of producing gasoline fractions therefrom. 'Thisapplication is adivision of my copending application, Serial No. 279,668, filed June 17, 1939 which, in turn,

earlier application, Serial No. 15. 1935, l

In a more specic sense the invention 'is concerned with the conversion of selected and limited fractions of such gases by a series of cooperative steps involving catalytic treatment and fracieos, filed April G. Alther, Chicago, lll ena! Oil Products Company, corporation of Delaware Application June 17, 1939,

hich is a continuation of application Serial 16,309, April 15, 1935. Divided and this application July 28, 1941, Serial No.

3 Claims. (Cl. 260483.15)

is a. continuation of my tionation. The process is particularly applicable -I to the treatment ofso-called propane-butane in the cracking of vheavier and less valuable portions of petroleums with the object of producing gasoline.

The term propane-butane fraction" refers to a particular group of hydrocarbons of'restricted boiling range including principally the paraiiin hydrocarbons. propane and the butanes and includes the corresponding oleilns of the same nux'nber of carbon atoms, that is, propylene and butylenes. The present process is a contribution toy processes aimed at the more efficient utilization of the propane-butano fractions as defined above, and the features and advantages of the process will be disclosed in the following specification.

In one specific embodiment the present invena tion comprises the polymerization of propanebutane fractions containing high percentages of readily poiymerized olens by contact with solid phosphoric acid catalysts, fractionation of the resulting 'products to produce tlxed gases, intermediate fractions comprising essentially unconverted propane and butanes and the corresponding olefin hydrocarbons. comprising unpolymerized propylene and butylenes which are returned for further polymerization, 'and gasoline boiling range liquid polymer fractions.-

According to the present invention the propane-butano fraction is defined as the intermediate hydrocarbon vfraction produced either from gases or from the stabilization olines which contain principally propane and the butanes and and the butylenes and also minor amounts of hydrocarbons of lessthan three carbon atoms comprising ethane, ethylene and methane and also the vapors of pentanes and amylenes.

The steps of the present process whereby .hy- -drocarbon mixtures comprising essentially those of 3 and 4 carbon atoms are converted into gasoline boiling range fractions of superior antilrnock of low boiling gas.

to 300 pounds per square material percentages of propylene asalgnor to Uni- Chicago, lli., a

serial No. statte.y

value may be conveniently described in connection with the attached drawing which shows diagrammatically in side elevation a plant hookup embodying the necessary interconnected units for accomplishing the objects of the invention. The drawing will be used todescribe a typical process flow but the scope of the invention is not limited in exact correspondence therewith since the relative sizes of units may be varied considerably `from the proportions shown in the drawing and since minor alterations in the flows and also such itemsas heat exchange may be introduced as found desirable or necessary. s

Referring to the drawing, a propane-butane fraction with considerable percentages of propylene, butylenes, and amylenes is passed through line 20 containing control valve 2| through a heating element 32V in furnace 23 to be brought up tothe temperature and pressure requisite to the emcient polymerization in the succeeding stage of the process. These temperatures will commonly be comprised within the range of 250 to 550 F., and the pressures maybe varied over a wide range since lpressure apparently has no 25 independent effect upon the polymerization reactions, although ordinarily pressures of about 100 inch are used. The heated vapors ofthe intermediate fraction then pass through line 24 containing control valve 25 andare subjected to the action of selected polymerizing catalysts in a series of towers 26, 29, and $2. The character of the catalyst'whlch it is preferred to use at this point is unique and it will be in point to devote some space to its description.

In general the catalysts employed mayI be des ignated as solid tained and then grinding the cake to produce filler. It is a feature this manner thatfor granular particles for tower of the catalysts prepared in most purposes the active acid constituent conportionrby weight of their stitutes the major weight. Thus the show as high as final catalyst granules may comprising of acid approaching the pyro acid.Y in composition and 40% ofcarrier. However. in the case of gas mixtures which contain very high percentages or easily polymerlzed olephosphoric acid catalysts.- These are prepared by -initlally incorporating relatively inert and usually siliand spacing materials,

'10% by weightof phosphoric` acid and it is common practice to employ mixes drating with steam,

. tive surface.

. dation followed taining control valve 28,

from which the xed fins, the percentage by weight of active acid may be reduced even as low as 30%.

The' carrying materials which are preferably employed in the manufacture of solid phosphoric acid catalysts include such materials as diatomaceous or nfusorial earths, artificially precipitated forms of silica, and aluminum silicates such as, for example, bentonites and montmorillonites representing members clay minerals. The diatomaceous earths are par`I ticularly suitable for this service.

In preparing the catalysts it is essential that the primary mixes o f carrier and acid be heated to .temperatures Within the approximate range ofl 480-570 F., to produce by dehydration the acid composition corresponding to maximum catalyzing effectiveness. `'Ihe acid vcomposition corresponds apparently to a ratio of phosphorus pentoxide to water slightly higher than thatA of pyrophosphoric acid, but owing to the diiiculties of analysis, the presenceof minor amounts of silicophosphoric acid` complexes and the diniculty of differentiating between combined and adsorbed water, it is identify the acid and reliance is therefore placed upon standardizing the method of preparation.

Advantages are sometimes gained by initially not possible to completely of the kaolin division ofH overheating and Yconsequently over-dehydrating l the absorbed acid and then .subsequently rehyas this apparently increases the porosity of the granules and hence their ac- The preferred type of contact polymerizing material gradually becomes fouled by deposition of heavy polymers and carbonaceous material but is readily regenerated at such times by air oxiby rehydration with steam if necessary.

The polymerizingunits have been shown in the drawing in series connection with the olefln containing gases from the first stage passing downwardly through catalyst beds in succession. The towers may also be connected in parallel to permit the alternate use and regeneration of their contained material. Furthermore, the drawing shows no provision for the removal of liquids which may separate at the temperature of operation of the towers and in some instances wherey in a'large amount of normally liquid materials is produced in the primary treating towers it may be best to remove condensates and prevent their--l further contact with catalyst, thus avoiding overpolymerization with the development of high boiling polymers and also preventing the wetting and contaminating o1' the succeeding catalyst f bed.

As shown in the drawing the heated gas mixtures from furnace 23 pass through line 24 containing controlA valve 25 downwardly through polymerizing tower 26, thence through line 21 conand downwardly through tower 29-and from there through line 3|)V containing control valve 3| through tower 32. Following the polymerizing step the total productsv then follow line 33 containing control valve 34 to a cooler 35 which is operated at the best temperature for enabling good separation of fixed gases and the cooled and partly liqueiled entering products leave taining control valve 4| containinglcon- 75 similar' processes trol valve 42 to mix with the gases from the final stabilizer. The liquids in separator 38 will now comprisepolymers of' substantially gasoline boiling range plus dissolved propane and butanes and some dissolved. propylene and butylenes.

The products are now nally stabilized to-produce a liquid polymer fraction. of proper vapor pressure and an overhead comprising' recyclestock and composed principally of ,3 and 4 car-` bon atom hydrocarbons. As before, stabilizer 45 which receives charge from line 43 containing control valve 44 may include the usual reboiling coils andprovision for recirculating a portion of the' overhead to control the distillation.

The overhead from stabilizer 45 passes through line 38 containing control `valve 40. and flows through the extension of rline 4|'through condenser 46 which is operated under suiciently low temperature to condense the light recycle stock which passes through line 4l containing controlI valve 48 to an intermediate accumulator 49 havi ther treatment. By following line 55 containing control valve 56 itv may be separately reheated in tubular heating element 51` arranged in fur-y after which the heated products may pass through line 6| containing control valve 62.

nace 58 to the entrance to the catalytic polymerizing units. 'Ihe temperatures and pressures for heating the recycle gases may thus be independently net effect on the quality controlled so that thev nal product is at an and quantity of the optimum.

If desired, the recycle stock may be passed by way of line 63 containing control valve 64 to the entrance of heater 22 along with the charge introduced through line 20. The return vof the recycle'stock serves to maintain a predetermined concentration of higher olens (propylene and butylenes) in the catalytic polymerizing operation.4

Liquid polymers constituting the major portion of the product of the process leave the bottom of stabilizer 45 through line 10 containing control valve 1| and pass through a cooler 12 after which they ow through line 13 containing control valve I4 to enter storage.

It will be evident fromthe preceding'description that, vWhile the characteristic features of the process are suiilc'ient to dene it, it possesses considerable exibilityin the polymerizing step and the recycling features. Owing to the general ilexibility the process is capable of lproducing some-i what variable results both as regards yield and quality of product. However, the following is 'selected from the available examples to indicate the general character of the results obtainable.

A propane-butane fraction subjected to polymerization had approximately 30% of olelns including propylene and higher land gave a yield of approximately 5 gallonsV of gasoline -boiling range liquids for 1000 cubic feet of the gas admitted to the polymerizing plant.

It will be evident from the foregoing specification and' example of the results obtained by the use of the process, that it is an improvement over in its field, .but at the same to be raised in temperature` time neither are to be construed in the light of imposing limitations upon the broad scope of the invention.

I claim as my invention:

i. In the production of polymerized olenns wherein a heated gaseous mixture containing a substantial amountof normally gaseous higher olefins is passed at a temperature not substanv tially in excess of about 550 F. in contact with a catalyst, the product oi the catalyzing operation is subjected to a stabilizing operation to form a.

liquid product and a composite normally gaseous product lean with respect to its content of higher olefins. the improvement which comprises returning at least a portion consisting of a controlled quantity of said composite lean gaseous product tially in excess of about 550 F. in contact with a catalyst and the product resulting from the .catalyzing operation is 4subjected. to fractional separation in a stabilizing chamber to form a liquid product and a composite normally gaseous product lean with respect to its content of higher i 3 olenns. the improvement which comprises ,withdrawing at least aiportion consistingof a conoieiins is maintained in the cataiyzing operation.

3. In the production oi polymerized oleilns wherein a heated gaseous mixture containing a substantial amount of normally gaseous higher oleiins is passed at a temperature not substan- 550 F. in contact with tially in excess of about a cataLvst and the product resulting from the catalyzing operation is subjected to fractional 'separation in a stabilizing chamber to forina liquid productand a composite normally gaseous product lean with respect to its coutent or higher olefins, the improvement which comprises-withdrawing at least a portion consisting oi.' a controlled quantity oi the composite lean normally gaseous product and returning said portion to the cataiyzing operation. being so regulated asto ,produce a predetermined concentration of higher olefins in the catalyzing operation.

JOSEPH G. ALTI-IER.

the return of said portion 

